The invention relates to a tool and method for producing a gear part having an external toothing.
In the following, the term xe2x80x9cwork piecexe2x80x9d relates to the blank which is to be machined or is partially machined. The term xe2x80x9ccompressingxe2x80x9d indicates a metal forming process which is used for the production of rotationally symmetrical bodies using pressing tools. In the art, the term xe2x80x9cshaping by rollingxe2x80x9d or xe2x80x9ccompression rollingxe2x80x9d is currently used for this method.
A tool of the above-mentioned type is described in German Patent Document DE 196 13 457 D1. The tool has several forming areas of increasing crown circles along a Yxe2x80x94Y axis. In this known arrangement, it is required that the forming tool or roller for each forming area not only move in the direction of the Y-axis, but the tool must also be moved back perpendicularly to the Yxe2x80x94Y axis. That is, the tool must be moved back radially, so that the next forming area can engage in the preformed tooth area of increased crown circle of the work piece.
In the case of this type of forming tool, the material of the work piece displaced by the tool is displaced into the space of the tooth to be formed, that is, into the space existing between the teeth of the tool. As a result, an unfolding or uncontrolled depositing of the displaced material of the work piece into the space of the tool occurs and thus within the tooth to be formed. The thus formed tooth in the work piece may have material deformations which are very difficult to control, such as folds or overlapping, and which can impair the stability of the tooth of the work piece to be produced.
It is an object of the invention to permit a production method as a result of a correspondingly constructed tool, in which an uncontrolled flowing of the displaced material does not occur in the area of the tooth to be formed, and which, in addition, avoids the additional movement of the forming roller previously required in the prior art.
It is also an object of the invention to suggest a method which permits a fast and cost-effective production of a gear part having an external toothing.
These objects, on which the invention is based, are achieved by a forming tool having several forming areas wherein the crown circle of the tool is the same for all forming areas and wherein different tooth depth of the forming areas is achieved by changing the root circle of the teeth of the tool.
In the arrangement according to the invention, the material of the work piece displaced by the teeth of the tool flows to the outside and can be removed therefrom after the completion of the gear wheel by a corresponding processing of the material.
According to the invention, the forming roller is disposed to be freely rotatable and therefore adapts without difficulty and gear-related couplings with the drive of the receiving tool to the teeth to be formed.
If required, it is naturally possible to insert a synchronous running device between the forming roller and the receiving tool.
In order to avoid an uncontrolled flowing of the material displaced by the teeth of the tool, it is further suggested according to the invention that a limiting device be provided at least in the edge area of the work piece. The limiting device is preferably formed by two interacting pressure rollers which hold the flowing-out material between one another, and optionally form and limit it.
In order to avoid a superfluous flowing-out of material, it is also suggested according to the invention that the circumferential area of the work piece to be deformed be optimized. For example, the circumferential area is curved concavely toward the inside or recessed by way of linear surfaces toward the inside, so that only as much material exists in the circumferential area of the work piece as is required for the forming of the actual tooth.
The method according to the invention is characterized essentially in that several forming rollers can simultaneously be used on the work piece. As a result, the pressure on the receiving tool, which occurs by pressing the forming roller into the work piece, is minimized because this pressure is absorbed by the optionally opposite forming roller.
Here, two, three or several forming rollers can be provided on the circumference of the work piece.
Finally, it is suggested according to the invention that the work piece is caused to carry out a rotating reciprocating movement, whereby the two flanks of the formed tooth are uniformly acted upon by the forming roller so that differences in the tooth flanks are avoided here.